Liquid crystal display devices have been widely used as television sets, personal computers, personal digital assistants (PDAs), and so forth because of their thinness, lightness, and low power consumption. In particular, there have recently been rapid advances in an increase in the size of liquid crystal display devices as typified by liquid crystal display devices for television sets. In the case of increasing the size, a multi-domain vertical alignment (MVA) mode is suitably used because even a large area can be produced in high yield and a wide viewing angle is provided. In the multi-domain vertical alignment mode, liquid crystal molecules are aligned perpendicularly to a substrate surface when a voltage is applied to a liquid crystal layer. It is thus possible to achieve high contrast, compared with a conventional twisted nematic (TN) mode.
In MVA mode, an alignment layer does not regulate the tilting direction of liquid crystal molecules. The tilting direction of liquid crystal molecules is determined by the effect of a protrusion (rib) composed of an insulating material, so there is no need to perform an alignment treatment step for the alignment layer. That is, static electricity and dust, which are generated by rubbing or the like, are not generated, thereby eliminating a cleaning step or the like after alignment treatment. Furthermore, the degree of nonuniformity of the initial tilt of liquid crystal molecules is low, which is effective in process simplification, yield improvement, and cost reduction.
In MVA mode, while there is no need for alignment treatment, it is necessary to form an undercoat layer corresponding to an alignment layer. The elimination of the undercoat layer is more preferred in light of the unevenness of the undercoat layer, the effect of contamination with foreign matter on the alignment of liquid crystal molecules, and an increase in the number of production steps and capital investment for the formation of the undercoat layer.
Meanwhile, a technique for imparting a pretilt angle by filling a liquid crystal composition containing a liquid crystal and a polymerizable component, such as a monomer or an oligomer (hereinafter, referred to as a monomer or the like), between substrates, and polymerizing the monomer or the like to form a polymer layer with liquid crystal molecules tilted by the application of a voltage between the substrates has recently been receiving attention (for example, see PTL 1). The liquid crystal exhibits a predetermined pretilt angle by the effect of the polymer layer even when the application of the voltage is stopped. Thus, the tilted direction of liquid crystal molecules is maintained without an alignment layer. The polymerization of the monomer or the like is performed by heat or irradiation with light (for example, ultraviolet rays).